The invention is directed to a method for manufacturing a brake shoe for drum brakes of motor vehicles.
Various methods for manufacturing a brake shoe are known. In a first, known method, a sheet metal member pre-shaped in the form of a circular arc is welded to an approximately sickle-shaped sheet metal web. This method has the disadvantage of requiring that two discrete parts must be positioned relative to one another and must then be welded. This, first, requiring relatively great labor input and, second, leading to the fact that a high dimensional precision is difficult to achieve. Moreover, a weld represents a possible weak point of the brake shoe that can lead to malfunctions during operation of the brake under unfavorable conditions.
Another known method proposes that two pre-shaped sheet metal members having a L-shaped cross section and the form of a circular arc be arranged back-to-back and be joined to one another by welding or riveting. In this method, too, a relatively high labor input is required and tight dimensional tolerances cannot be observed. Moreover, a brake shoe manufactured in this way is relatively heavy since a relatively great quantity of sheet metal material is utilized, particularly in the region of the rib which, of course, is double-layer.
A third known method is the manufacture of brake shoes of cast iron or light metal in a casting process, whereby the manufacturing cost, however, is extremely high as a consequence of the required casting molds. What is thereby also disadvantageous is that cast brake shoes are subject to a higher risk of breakage than brake shoes composed of sheet metal.
It would be an advance in the art if there were provided a method for manufacturing a brake shoe of the type described above in which a stable and reliable and, at the same time, lightweight brake shoe could be manufactured with reasonable manufacturing cost.